Telephone pole-piece



(No Model.) T. A. WATSON.

TELEPHONE POLE PIECE. No. 251,326. l Patented Dec. 20,1881.

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NITED STATES PATENT Ormea.

THOMAS A. \VATSON, OF EVERETT, ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

TELEPHONE POLE-PIECE.

SPECIFICATION forming part of Letters Patent No. 251,326, dated December 20, 1881.

Application led April 29, 1880. (No model.)

1" o all whom it may concern:

Be it known that I, THOMAS A. WATsoN, of Everett, county of Middlesex, State of Massachusetts, have invented an Improvement in Telephone Pole-Pieces, of which the following description, in connection with the accompanying drawings, is a specification.

My invention relates to pole-pieces for magnets, and is shown embodied in a pole-piece fora compound telephone such as described in another application tiled by me herewith.

As usually constructed, the pole-piece of a telephone, or the core of the small electro-magnet attached to the end ot' and polarized by a permanent magnet, is a small cylinder of iron surrounded by the induetioncoils.

As the electric current in -an induction-coil has the strongest effect in the layers ot' wire nearest the core, it is obvious that the effect will be increased by bringing as large a portion of the said coils as possible next to the surface of the core or pole-piece. This I accomplish in accordance with my invention by the employment, in addition to the usual central core surrounded by'an induction-coil, of a second pole-projection surrounding the ,said coil, and consequently adjacent to the outer helices of the said coil, and, as herein shown, a series of the said pole-projections are arranged as a series of annular rings concentric with the usual central cylindrical core, the coils lying in the annular space between the said pole-projections, which are all connected with a disk of soft iron, which may be attached to the end of the usual permanent magnet of a magneto-telephone.

It will be readily understood that a polepiece of this sort is especially adapted for use in a compound telephone such as described in my other application,wherein a series of circuits or groups of circuits are connected with separate and independent induction-coils in a telephone with a single sound chamber and passage; and when the pole-piece of the present invention is employed the separate coils may be placed each in a separate annular channel between two pole-projections, or they may be wound side by side, each separate coil then filling a portion of each and all of the said annular spaces.

Figure 1 is a top view of the pole-piece embodying my invention; Fig. 2, a side view thereof, and Fig. 3 a longitudinal section of the'upper portion of a telephone provided with one of lthe said pole-pieces.

The pole-piece consists of the usual central core, a, connected with a circular plate, b, adapted to be attached in any convenient manner to the permanent magnet c. Connected with the plate b are two other pole-projections, c d, (shown as series of pins arranged in circles concentric with the central core, a.) Making the pole-projections c d as a series of pins enables them to be easily connected with the plate b, they being merely inserted with a tight iit in a series of holes drilled or punched in the said plate.

It is obvious that the pole-projections c d may be made as solid rings or tubes, and that they may be of any desired shape. The coils cfg are placed in the spaces between and around the pole-projections a c d, thus being in the most favorable position to enable the electric currents in the said coils to have as strong an effect as possible upon the said polepiece.

When desired for use in an ordinary telephone, the coils may all form one continuous circuit from 2 to 5, being connected as shown by the dotted lines 3 4, Fig. 1; or, if the instrument is intended to be used asa compound telephone with separate coils in independent circuits, each spool cfg may contain an independent coil, as indicated by the lines 9, 7 8, and 2 6; or the independent circuit-coils may be Wound side by side, each spool containing a portion of each coil and each coil occupying a portion of each and all of the spools.

In Fig. 3 the magnet and compound polepiece and coils are shown inclosed in a common telephone-case provided with a diaphragm and single sound-passage.

It is obvious that a pole-piece made as herein described also affords a much larger surface to act upon and be acted upon by the diaphragm of the telephone.

I claiml.-An electro-magnet for telephones, comprising a permanent magnet, a number ot' concentric pole-pieces of soft iron, and insulated IOO wire coiled in tbe spaces between said polepieces, substantially as described.

2. The combination, in a telephone, of the diaphragm and an electro-magnet having a number of concentric soft-iron pole-pieces, with insulated wire coiled in the spaces between the said soft-iron pole-pieces, substantially as described.

3. The herein-described pole-piece, consisting of a plate provided with a series of' poleprojections7 made as concentric or parallel rows of pins, inserted in the said plate and adapted to receive coils of insulated wire between the said rows, substantially as described.

4. In a compound telephone, a series of concentric helices of insulated wire connected in separate circuits, and combined with polepieces and a diaphragm, substantially as described.

In testimony whereofI have signed my name to this specification in the presence of two subscribing witnesses.

y THoMAs A. wATsoN.

Witnesses Jos. P. LIVERMORE, N. E. G, WHITNEY. 

